O O + + O O 2 3 4 5 1) Institute of Biology and Chemistry, Catholic University, Campinas, Sao Paolo, 13020 904, Brazil, e-mail: dalmo.mandelli@uol.com.br; 2) Institute of Chemistry, State University, Campinas, Sao Paolo, 13083 970, Brazil, e-mail: ulf@iqm.unicamp.br; 3) N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow 119991, fax (7095) 137 61 30, e-mail: shulpin@chph.ras.ru. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 203-205, May- June, 2002. Original article submitted May 23, 2002. 0009-3130/02/3803-0243$27.00 2002 Plenum Publishing Corporation © 243 Chemistry of Natural Compounds, Vol. 38, No. 3, 2002 HYDROGEN-PEROXIDE EPOXIDATION OF NATURAL OLEFINS CATALYZED BY A DINUCLEAR MANGANESE COMPLEX D. Mandelli, K. B. Voitiski, U. Schuchardt, UDC 547.918 1 1 2 and G. B. Shul′pin 3 The complex of Mn(IV) with the macrocyclic N-containing ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (L) [L Mn O ](PF ) catalyzes epoxidation of (+)-limonene in CH CN solution at room temperature. Adding 2 2 3 62 3 CH COOH accelerates the reaction. The products are isomers of limonene epoxide with predominance of 3 that with an epoxified ring double bond. Epoxidation of α- and β-pinene by this system is less effective, apparently due to extensive steric shielding of the double bonds in the pinenes. Key words: terpenes, limonene, pinene, epoxidation, catalysis, hydrogen peroxide, manganese complexes. Oxidation, in particular, the epoxidation of terpenes that is observed in many Brazilian tropical and subtropical plants, is an important process from a practical viewpoint because the products are valuable starting materials for the synthesis of fragrances and drugs [1]. The dinuclear complex of Mn(IV) with the macrocyclic N-containing ligand 1,4,7-trimethyl-1,4,7- triazacyclononane (L) [L Mn O ](PF ) (1) catalyzes oxidation of saturated hydrocarbons, secondary alcohols, and sulfides by 2 2 3 62 H O in CH CN at room or even reduced temperature [2-7]. An organic acid, in particular, acetic, is mandatory. 2 2 3 We investigated oxidation by the above system of certain natural terpenes such as (+)-limonene (2) and α- and β-pinene (6 and 9, respectively). We have found that the hydrocarbon is practically inactive in the absence of a small quantity of acetic acid. Epoxidation of limonene, which contains two different double bonds, gives products of addition to both the internal ring double bond and the double bond in the side chain (Table 1). The first product dominates. The ratio 3/4 varies from 1.4 (expt. No. 7), to 3.5 (expt. No. 9) depending on the reagent concentrations and the reaction time. The unoptimized maximum yield of both monoepoxides was almost 50% based on starting limonene. Use of an excess of H O and a short reaction time 2 2 formed in significant quantities the product of double epoxidation at both double bonds (5) (expts. No. 8, 9, and 10). The overall yield of epoxides was >75% based on starting limonene. Another product of unknown structure (the concentration of which in Table 1 is denoted by [x]) was formed in several experiments (4, 8, 9, 10). However, the amount of it was much less than those of the target epoxides (GC).